Datasheet

LPC11E3X All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 2.3 — 11 September 2014 54 of 71
NXP Semiconductors
LPC11E3x
32-bit ARM Cortex-M0 microcontroller
11.2 XTAL Printed-Circuit Board (PCB) layout guidelines
Follow these guidelines for PCB layout:
• Connect the crystal on the PCB as close as possible to the oscillator input and output
pins of the chip.
• Take care that the load capacitors C
x1
, C
x2
, and C
x3
in case of third overtone crystal
use have a common ground plane.
Fig 27. Oscillator modes and models: oscillation mode of operation and external crystal
model used for C
X1
/C
X2
evaluation
Table 17. Recommended values for C
X1
/C
X2
in oscillation mode (crystal and external
components parameters) low frequency mode
Fundamental oscillation
frequency F
OSC
Crystal load
capacitance C
L
Maximum crystal
series resistance R
S
External load
capacitors C
X1
, C
X2
1 MHz to 5 MHz 10 pF < 300  18 pF, 18 pF
20 pF < 300  39 pF, 39 pF
30 pF < 300  57 pF, 57 pF
5 MHz to 10 MHz 10 pF < 300  18 pF, 18 pF
20 pF < 200  39 pF, 39 pF
30 pF < 100  57 pF, 57 pF
10 MHz to 15 MHz 10 pF < 160  18 pF, 18 pF
20 pF < 60  39 pF, 39 pF
15 MHz to 20 MHz 10 pF < 80  18 pF, 18 pF
Table 18. Recommended values for C
X1
/C
X2
in oscillation mode (crystal and external
components parameters) high frequency mode
Fundamental oscillation
frequency F
OSC
Crystal load
capacitance C
L
Maximum crystal
series resistance R
S
External load
capacitors C
X1
, C
X2
15 MHz to 20 MHz 10 pF < 180  18 pF, 18 pF
20 pF < 100  39 pF, 39 pF
20 MHz to 25 MHz 10 pF < 160  18 pF, 18 pF
20 pF < 80  39 pF, 39 pF
002aaf424
LPC1xxx
XTALIN XTALOUT
C
X2
C
X1
XTAL
=
C
L
C
P
R
S
L